The electronics, display and energy industries rely on the formation of coatings and patterns of conductive materials to form circuits on organic and inorganic substrates. The primary methods for generating these patterns are screen printing for features larger than about 100 μm and thin film and etching methods for features smaller than about 100 μm. Other subtractive methods to attain fine feature sizes include the use of photo-patternable pastes and laser trimming.
One consideration with respect to patterning of conductors is cost. Non-vacuum, additive methods generally entail lower costs than vacuum and subtractive approaches. Some of these printing approaches utilize high viscosity flowable liquids. Screen-printing, for example, uses flowable mediums with viscosities of thousands of centipoise. At the other extreme, low viscosity compositions can be deposited by methods such as ink jet printing. However, low viscosity compositions are not as well developed as the high viscosity compositions.
Ink jet printing of conductors has been explored, but the approaches to date have been inadequate for producing well-defined features with good electrical properties, particularly at relatively low temperatures.
There exists a need for compositions for the fabrication of conductive features for use in electronics, displays, and other applications. Further, there is a need for compositions that have low processing temperatures to allow deposition onto organic substrates and subsequent thermal treatment. It would also be advantageous if the compositions could be deposited with a fine feature size, such as not greater than about 100 μm, while still providing electronic features with adequate electrical and mechanical properties.
Further, there is a need for electronic circuit elements and complete electronic circuits fabricated on inexpensive, thin and/or flexible substrates, such as paper, using high volume printing techniques such as reel-to-reel printing. Recent developments in organic thin film transistor (TFT) technology and organic light emitting device (OLED) technology have accelerated the need for complimentary circuit elements that can be written directly onto low cost substrates. Such elements include conductive interconnects, electrodes, conductive contacts and via fills.